This represents a SQLObject class that is bound to a specific
connection (instances have a connection instance variable, but
classes are global, so this is binds the connection variable
lazily when a class method is accessed)

This object serves as a hub for connections, so that you can pass
in a ConnectionHub to a SQLObject subclass as though it was a
connection, but actually bind a real database connection later.
You can also bind connections on a per-thread basis.

You must hang onto the original ConnectionHub instance, as you
cannot retrieve it again from the class or instance.